Now its an interesting find....the JL 137AE with Fs 23 Hz , Xmax 23 mm and 1500 W RMS intended for car use (800 GB pounds) is being used as dual pair in JL 213 ( 12000 USD).. goes with class A/B 3500 watt RMS.
Its a 13.5 inch driver

Now its twice as expensive as the ASW 855 subwoofer driver i.e 400 GBP and the subwoofer unit i.e 3000 GBP, it goes with 1000 watts RMS.Its a 15 inch driver.

I want to go DIY route 2 pairs of any of them ... a huge investment so wanted to sure which way to go.... i have 4x A/B bridged amplifiers for 1500 Watts into 8ohm so amplification and equalization is not an issue , no D class route.

Objective: lowest octave, high SPL out standing SQ without any hint of distortion may even go pull push route . advice please

The drivers in their home subs are not exactly the same as the car versions. When they first came out with their home subwoofers, their owner came on some of the forums & mentioned that the 13w7's had been "tweaked" for home use. He didn't say, of course, how they are different. Can't be worth $12,000 different! The problem you may run into is their 3 ohm impedance with some of the pro amps out there. Shouldn't be a problem if you bridged your amp & ran them in series.

intend to use them with krell 700 CX, so around 1400 watts per channel would be available at 4 ohm.
Yes i have thought about TC sounds LMS ultra 5400 , it should be pretty loud given its size and its about 900 USD which is cheaper than 800 GBP JL 13W6 which is around 1200 USD but its 13.5 inch versus 18 inch , an X Linear as compared to Xmax , hence the issue of sound quality....????

2 channel... i have 2x HT subwoofers diy made from 15 inch paradigm servo subwoofer driven by peavey GPS-2600 pro amp which is 600 watts into 8 ohms. BTW i have compared the sub with krell fpb-600,class A amp, and Belcanto 500 class D amplifier, all set below 80 hz. i tell u class D is the lousiest at even moderate power levesl, bass seems to be looooooose so much harmonic distortion lack of woofer control, Peavey class A/B is acceptable below 50 Hz.

So based on my experience i want multiple subs like 4 drivers preferablu 15 inch , sealed powered class A amp , run with B&W 802d full range, which are al krell , so it b run by krell 600 so another reason to go with krell ..tone , timbre, slew rate matching with the smaller dual 8 inch drivers . thats why i wanted to go for B&W 15 inch drivers set up as dual L+R pairs on each side of B&W 802.

you can think of it actually as 4 way system with dual 15 inch woofers to minimize distortion by excursion and and better sensitivity matching with the mains....